The inventors disclosed a general structure of a chip-like network resistor in Japanese Patent Application Laid-Open Publication No. 78701/1995. The chip-like network resistor disclosed in the publication includes an insulating substrate which is formed on each of both ends thereof with a plurality of recesses, a plurality of thick-film electrodes arranged adjacently to the recesses, and resistance elements each arranged between each pair of thick-film electrodes. Also, the resistor includes terminal electrodes each are arranged so as to cover an inner surface of the recess and connected to the thick-film electrode corresponding thereto. The terminal electrodes each include a thin metal film electrode layer and a plated electrode layer of a two-layer structure arranged so as to cover the thin metal film electrode layer. The thin metal film electrode layer includes a front surface electrode section formed on a front surface of the insulating substrate so as to overlap with the thick-film electrode, a side surface electrode section connected to the front surface electrode section and arranged so as to cover a whole inner surface of the recess and a rear surface electrode section connected to the side surface electrode section and arranged on a rear surface of the insulating substrate.
Conventionally, manufacturing of such a resistor is carried out by first providing a large-sized insulating substrate which is formed on a front surface thereof with lattice-like separation grooves constituted of a plurality of longitudinal grooves and a plurality of lateral grooves. Also, the insulating substrate is formed with a plurality of through-holes of a circular shape in cross section, each of which is arranged along a portion of the lateral groove positioned between each adjacent two of the longitudinal grooves. Thereafter, the large-sized insulating substrate is formed on the front surface thereof with a plurality of thick-film electrodes (primary electrodes), which are positioned on regions each interposed between each adjacent two of the lateral grooves and between each adjacent two of the longitudinal grooves while being in proximity to each of the through-holes. Then, the regions each are formed thereon with a plurality of resistance elements in a manner to extend between two of the thick-film electrodes opposite to each other, followed by covering of the resistance elements with a glass coating. Then, a resistance of the resistance element is measured by means of a probe electrode for measurement which is kept contacted at a distal end or tip thereof with the thick-film electrodes positioned on both sides of the resistance element. Then, laser trimming is carried out depending on the resistance measured, to thereby adjust the resistance to a desired value. After the trimming, the glass coating is covered with glass or resin. Then, the through-holes each are covered at both ends and an inner surface thereof with a thin metal film and then the large-sized insulating substrate is separated into a plurality of chip-like elements along the longitudinal and lateral grooves. Lastly, the chip-like elements each are subject on an electrode section thereof to plating.
The separation of the substrate into the chip-like elements causes the through-holes to be cut, leading to formation of the recesses and thin metal film electrode layer described above. The front surface electrode section of the thin metal film electrode layer is merely required to permit the thick-film electrode and side surface electrode section to be connected to each other, thus, the prior art does not pay any specific attention to a configuration of the front surface electrode section. Therefore, the conventional resistor is not constructed in such a manner that the front surface electrode section is arranged so as to fully surround a circumference or periphery of an opening of the recess defined in a thickness direction of the insulating substrate.
Such construction of the conventional resistor does not cause any serious problem so long as the resistor is formed into a large size. However, a reduction in size of the chip-like resistor causes the components thereof to be reduced in size correspondingly, to thereby render adjustment of the resistance by trimming highly troublesome. Also, a reduction in resistance of the resistance element causes a variation in resistance of the terminal electrode to substantially affect a resistance of the resistance element. Unfortunately, the conventional resistor causes a variation in resistance of the terminal electrode to be increased. Also, a decrease in size of the chip-like resistor substantially fails to increase a distance between the electrodes adjacent to each other. Further, the conventional resistor causes a corner of each of the recesses to be readily broken when the large-sized insulating substrate is separated into the individual chip-like elements.
It is an object of the present invention to provide a chip-like network resistor which is capable of minimizing a variation in resistance of terminal electrodes.
It is another object of the present invention to provide a chip-like network resistor which is capable of effectively preventing positional deviation thereof during soldering thereof onto an electrode on a circuit board.
It is a further object of the present invention to provide a chip-like network resistor which is capable of minimizing a variation in dimension or distance between electrodes adjacent to each other.
It is still another object of the present invention to provide a chip-like network resistor which is capable of facilitating measurement of a resistance during trimming.
It is a still further object of the present invention to provide a chip-like network resistor which is capable of minimizing breakage of a corner of a recess when a large-sized insulating substrate is cut.